Monitoring opacity of smoke exhausted by wood stove and controlling wood stove based on same

ABSTRACT

A wood stove monitoring and control device can include a mounting flange mountable to a chimney exhaust pipe of a wood stove. The device can include a ring removably mountable on top of the mounting flange, where the flange is suitably positioned vertically along the exhaust pipe so that the ring is positioned at least partially above an end of the exhaust pipe. The device includes an optical beam source disposed on the ring, and which generates and outputs an optical beam. The device includes an optical sensor positioned on the ring opposite the optical beam source to detect the optical beam output by the optical beam source as the optical beam passes through smoke exhausted by the wood stove through the exhaust pipe. The device can include a temperature probe disposed on the ring to measure a temperature of heat exhausted by the wood stove through the exhaust pipe.

RELATED APPLICATIONS

The present patent application is a continuation of the patentapplication filed on Jan. 25, 2018, and assigned patent application Ser.No. 15/880,033, which itself claims priority to the provisional patentapplication filed on Jan. 26, 2017, and assigned patent application No.62/450,794, both of which are hereby incorporated by reference.

BACKGROUND

There are different options that people can choose from to heat theirhomes. One traditional but still popular way to heat one's home is awood-burning stove. A wood-burning stove uses an inherently renewableenergy source, the wood from trees, which is burned in the stove togenerate heat within a home. The smoke that a wood stove generates canbe exhausted actively or passively through a chimney.

SUMMARY

An example wood stove monitoring device includes a mounting flangemountable to and fittable over a chimney exhaust pipe of a wood stove.The mounting flange is movably positionable vertically along the chimneyexhaust pipe. The monitoring device includes a ring removably mountableon top of the mounting flange. The ring has an interior surface andexterior flat surfaces. The mounting flange is suitably positionablevertically along the chimney exhaust pipe so that the ring is positionedat least partially above an end of the chimney exhaust pipe. Themonitoring device includes an optical beam source disposed on a firstexterior flat surface of the exterior flat surfaces of the ring. Theoptical beam source generates and outputs an optical beam perpendicularto the first exterior flat surface and through a corresponding holewithin the first exterior flat surface and the interior surface of thering.

The example wood stove monitoring device includes an optical sensordisposed on a second exterior flat surface of the exterior flat surfacesof the ring opposite to the first exterior flat surface. The opticalsensor is linearly aligned with the optical beam source to detect theoptical beam output by the optical beam source as the optical beampasses through smoke exhausted by the wood stove through the chimneyexhaust pipe. The monitoring device includes a temperature probedisposed on a third exterior flat surface of the exterior flat surfacesof the ring and extending through the third exterior flat surface andthe interior surface of the ring. The temperature probe measures atemperature of heat exhausted by the wood stove through the chimneyexhaust pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings referenced herein form a part of the specification.Features shown in the drawing are meant as illustrative of only someembodiments of the invention, and not of all embodiments of theinvention, unless otherwise explicitly indicated, and implications tothe contrary are otherwise not to be made.

FIG. 1 is a diagram of an example mounting flange of a wood stovemonitoring device.

FIG. 2 is a diagram of an example ring of the wood stove monitoringdevice.

FIG. 3 is a diagram of an example thermal energy generation (TEG) stackof the wood stove monitoring device.

FIG. 4 is a diagram of an example optical beam source, optical sensor,and processing hardware and temperature probe enclosure of the woodstove monitoring device.

FIG. 5 is a diagram of an example temperature probe of the wood stovemonitoring device.

FIG. 6 is a block diagram of an example processing hardware enclosure ofthe wood stove monitoring device.

FIG. 7 is a diagram of an example calibration mechanism of a wood stovemonitoring device.

FIG. 8 is a diagram of an example calibration wheel of a calibrationmechanism of a wood stove monitoring device.

FIG. 9 is a diagram of an example wood stove monitoring device mountedto a chimney exhaust pipe of a wood-burning stove.

FIG. 10 is a flowchart of an example method for controlling awood-burning stove using a wood stove monitoring device.

DETAILED DESCRIPTION

In the following detailed description of exemplary embodiments of theinvention, reference is made to the accompanying drawings that form apart hereof, and in which is shown by way of illustration specificexemplary embodiments in which the invention may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the invention. Other embodiments may be utilized,and logical, mechanical, and other changes may be made without departingfrom the spirit or scope of the present invention. The followingdetailed description is, therefore, not to be taken in a limiting sense,and the scope of the embodiment of the invention is defined only by theappended claims.

As noted in the background section, houses can be heated usingwood-burning stoves. A difficulty with using a wood stove is that if thewood stove is not properly operated and monitored during operation, thewood stove can generate smoke. Many jurisdictions have recognized smokeas a regulated pollutant, to the extent that in certain weatherconditions, “no burn days” or “burn bans” are put into effect, limitingthe usage of wood-burning stoves.

Furthermore, many jurisdictions have rules in place as to the length oftime that a wood-burning stove can generate smoke containing undesiredpollutants, such as opaque smoke particles. Such restrictions aregenerally in the form of smoke minutes. A smoke minute may be defined asa smoke reading that exceeds a threshold opacity, such as 20%, for morethan one minute.

A difficulty with using a wood-burning stove is that the operator, whois typically located in the house in which the wood stove is located,has no way of monitoring the opacity of the smoke that the stove isexhausting through a chimney. Therefore, the operator may be satisfiedwith the wood stove's operation in terms of heat generated, withoutrecognizing that the stove is generating impermissible pollution in theform of smoke. Furthermore, even if a wood stove is not currentlygenerating impermissible pollution, if the operator does not at leastperiodically tend to the fire within the stove by adding fuel in theform of wood or by controlling the air-fuel mixture by controlling anair intake of the stove, the wood stove can later generate undesiredpollution.

Disclosed herein are example wood stove monitoring devices that canmonitor the smoke exhausted by a wood stove and that can be used tocontrol operation of the stove. An example stove monitoring device caninclude an optical beam source to generate and output an optical beamthrough smoke exhausted by a wood stove via a chimney exhaust pipe. Thedevice can include an optical sensor to detect the optical beam outputby the optical beam source as the optical beam passes through the smoke,and processing hardware to correlate the optical beam through the smokeas detected by the optical sensor to an opacity of the smoke exhaustedby the wood stove.

The device can include a temperature probe to measure a temperature ofheat exhausted by the wood stove through the chimney exhaust pipe. Assuch, the processing hardware can generate a fresh air intake controlsignal based on the correlated opacity and the measured temperature.This control signal can control a fresh air intake mechanism of the woodstove to control opacity of the smoke exhausted by the wood stove. Themonitoring device can include communication hardware to transmit thesignal to the fresh air intake mechanism of the wood stove. The controlsignal may additionally or alternatively control a thermal oxidizer orother smoke reduction technology mechanism, present at the chimney or atthe stove itself, to engage to reduce the opacity of the smoke. Suchmechanisms therefore can be controlled based on the generated controlsignal to regulate the opacity of the exhausted smoke.

In addition to or in lieu of generating the fresh air intake controlsignal, and transmitting the signal to the fresh air intake mechanism ofthe wood stove, the wood stove monitoring device can also inform anoperator of the stove of the opacity of the smoke that the stove isexhausting. The monitoring device may inform the operator periodically,or just when the opacity of the smoke exceeds a predetermined threshold,such as a threshold corresponding to a percentage of the legallypermissible opacity limit. The monitoring device may inform the operatorvia email, text message, or in another manner, such as via a dedicatedsmartphone app notification. The operator may be also be informed whenthe temperature of the exhausted smoke drops below a predeterminedthreshold temperature, and in this respect may be instructed to add fuel(i.e., wood) to the fire burning in the stove to increase thetemperature.

FIG. 1 shows an example mounting flange 104 of a wood stove monitoringdevice. The mounting flange 104 is mounted to and fitted over a chimneyexhaust pipe 102 of a wood-burning stove, where the exhaust pipe 102 hasa top end 106. The mounting flange 104 is movably positionablevertically along the pipe 102. For instance, the mounting flange 104 maybe fitted over the pipe 102, and then placed at a desired positionvertically along the pipe 102, before the flange 104 is then affixed tothe pipe 102. The flange 104 may be secured to the pipe 102 via ascrew-set clamp, magnets, or in another manner. The example mountingflange 104 can also include multiple magnets 108 on a top surfacethereof, uniformly or otherwise disposed along a perimeter of the flange104.

FIG. 2 shows an example ring 202 of a wood stove monitoring device. Thering 202 is removably mountable on top of the mounting flange 104. Forinstance, the ring 202 may be secure to the flange 104 via the magnets108 of the flange 104. The mounting flange 104 is suitably positionedvertically along the chimney exhaust pipe 102 so that the ring 202 is atleast partially above the top end 106 of the exhaust pipe 102. The ring202 includes an interior surface 204 that corresponds to the outer shapeof the exhaust pipe 102, such as circular or round in FIGS. 1 and 2. Thering 202 also has multiple exterior flat surfaces 206. In the example ofFIG. 2, there are six surfaces 206, such that the ring 202 is hexagonalin shape. In other implementations, there may be fewer or more than sixsurfaces 206, including an implementation in which there are eightsurfaces 206, in which case the ring 202 is octagonal in shape. The ring202 includes a thermal energy generation (TEG) stack 208 disposed on aparticular exterior flat surface 206, which generates electrical powerfrom the heat exhausted by the wood stove through its chimney exhaustpipe 102.

FIG. 3 shows an exploded side profile of an example TEG stack 208 indetail. The TEG stack 208 includes a thermal energy generator 302 thatconverts the heat exhausted by the wood stove to electrical power. Thestack 208 includes a regulating heat transfer plate 304 and shims 306.The shims 306 are adjacent to the particular exterior flat surface 206of the ring 202, and thus are disposed between the thermal energygenerator 302 and the regulating heat transfer plate 304. The regulatingheat transfer plate 304 includes cooling channels 312.

As such, heat exhausted by the wood stove is conductively transferred tothe thermal energy generator 302 from the ring 202 via the shims 306 andthe heat transfer plate 304. The shims 306 and the heat transfer plate304, the latter via the cooling channels 312, reduce the temperature ofthe heat conductively transferred to the generator 302 so that thethermal energy generator 302 does not receive excessive thermal energy.The TEG stack 208 also includes a passive heat sink 308 which drawsexcessive heat from the generator 302, and which is subsequently removedvia a fan 310. That is, the passive heat sink 308 draws excessive heatfrom the generator 302 conductively, and the fan 310 removes theexcessive heat via forced convection. The heat sink 308 and the fan 310can be said to constitute a cooling mechanism of the stack 208.

FIG. 4 shows an example optical beam source 404 and an optical sensor402 of a wood stove monitoring device. The optical beam source 404 isdisposed at a given exterior surface 206 of the ring 202, and theoptical sensor 402 is disposed at an opposite exterior surface 206 ofthe ring 202. The TEG stack 208 is also depicted in FIG. 4.

The optical beam source 404, such as a laser, generates and outputs anoptical beam 406, such as a laser beam, perpendicular to the exteriorsurface 206 at which the source 404 is mounted, and through acorresponding hole 408 within this exterior surface 206 and the interiorsurface 204 of the ring. The optical sensor 402 is linearly aligned withthe optical beam source 404 to detect the optical beam 406 output by theoptical beam source 404 as the beam 406 passes through smoke exhaustedby the wood stove through the chimney exhaust pipe 102 of FIG. 1.

A processing hardware enclosure 410 is also depicted in FIG. 4. Theenclosure 410 is disposed at another exterior surface 206 of the ring202, and encloses processing and other hardware that is communicativelyconnected to the optical beam source 404 and the optical sensor 402. Theprocessing and other hardware within the enclosure 410, as well as theoptical beam source 404 and/or the optical sensor 402, can receive powergenerated by the TEG stack 208, and therefore may be conductivelyconnected to the TEG stack 208.

FIG. 5 shows a cross-sectional side view of an example temperature probe502 of a wood stove monitoring device. The temperature probe 502 ismounted at a specific exterior surface 206 of the ring 202, and extendsthrough this exterior surface 206 and through the interior surface 204of the ring 202. The temperature probe 502 can thus measure thetemperature of heat exhausted by the wood stove through the chimneyexhaust pipe of FIG. 1. The temperature probe 502 may also be powered bythe power generated by the TEG stack 208. For instance, the temperatureprobe 502 may be indirectly powered by the power generated by the TEGstack 208. As an example, the TEG stack 208 may power a microcontroller,which is generally described as processing hardware later in thedetailed description, and the temperature probe 502 then receiving a setvoltage from the microcontroller. In such instance, the temperatureprobe 502 may be a thermocouple, for instance.

FIG. 6 shows a block diagram of an example processing hardware enclosure410 of a wood stove monitoring device. The enclosure 410 enclosesprocessing hardware 602 and communication hardware 604. The processinghardware 602 can include a processor and a non-transitorycomputer-readable data storage medium that stores program codeexecutable by the processor, an application-specific integrated circuit(ASIC), or other processing hardware. The communication hardware 604 caninclude wireless communication hardware, such as Wi-Fi, mobile telephony(e.g., LTE), Bluetooth, or other wireless communication hardware. Thehardware 602 and 604 can be powered by the TEG stack 208 of FIG. 2, andtherefore may be conductively connected to the stack 208.

The processing hardware 602 can correlate the optical beam 406 asdetected by the optical sensor 402 to the opacity of the smoke exhaustedby the wood stove through the chimney exhaust pipe 102. The processinghardware 602 may further generate a fresh air intake control signalbased on this correlated opacity and the temperature of the smokeexhausted by the wood stove through the chimney exhaust pipe 102 asmeasured by the temperature probe 502. The processing hardware 602 maycontrol a fresh air intake mechanism of the wood stove, viacommunicating the control signal to the wood stove using thecommunication hardware 604, where the control signal may control adamper that adjusts how much fresh air is input into the stove. Thecontrol signal is generated to maintain or adjust the smoke exhausted bythe wood stove so that the opacity thereof is below a threshold level.The control signal may additionally or alternatively control a thermaloxidizer or other smoke reduction technology mechanism, present at thechimney or at the stove itself, to engage to reduce the opacity of thesmoke, as noted above. Furthermore, the processing hardware 602 mayalso, using the communication hardware 604, notify an operator of thewood stove of the opacity of the smoke being exhausted, such as when theopacity is greater than the threshold level.

FIG. 7 shows a cross-sectional side view of an example calibrationmechanism of a wood stove monitoring device. The calibration mechanismcan be made up by a calibration wheel 702 and a calibration motor 704.The motor 704 is attached to the exterior surface 206 of the ring 202 towhich the optical sensor 402 is attached via, for instance, a mountingarm 706. The calibration wheel 702 is rotatably mounted to the motor704. Therefore, the motor 704, which may conductively be connected toand be powered by the TEG stack 208 of FIG. 2, can rotate thecalibration wheel 702. The wheel 702 is disposed within an optical pathof the optical sensor 402, so that a region of the wheel 702 is inoptical interference with the sensor 402 receiving the optical beam 406output by the optical beam source 404 of FIG. 4 through the smokegenerated by the wood stove. The region of the wheel 702 that is incurrent optical interference with the sensor 402 is controlled rotationof the wheel 702 by the motor 704.

FIG. 8 shows an example calibration wheel 702 of a calibration mechanismof a wood stove monitoring device. The calibration wheel 702 includes atransparent region 802 and semi-opaque regions 804A, 804B, and 804C,which are collectively referred to as the semi-opaque regions 804.During regular operation of the wood stove monitoring device in whichthe device is actively being used to detect the opacity of the smokeexhausted by the wood burning stove through the chimney exhaust pipe102, the motor 704 rotates the wheel 702 so that the transparent region802 is in optical interference with the optical sensor 402 receiving theoptical beam 406.

By comparison, when the wood stove is not in active use, the wood stovemonitoring device may be periodically calibrated by the optical sensor402 detecting the optical beam 406 through the different semi-opaqueregions 804. Each region 804 has a different prespecified opacity. Themotor 704 rotates the wheel 702 so that a given region 804 is in opticalinterference with the optical sensor 402 receiving the optical beam 406.The value measured by the optical sensor 402 thus is corresponded to theprespecified opacity of the region 804 in question. This process isrepeated for each different semi-opaque region 804. Therefore, thevalues that the optical sensor 402 outputs can be calibrated so thatwhen wood burning stove is subsequently used, the opacity of thegenerated smoke is properly determined from the value measured by theoptical sensor 402 for the optical beam 406 through the smoke.

FIG. 9 shows an example wood stove monitoring device 900. The wood stovemonitoring device 900 includes the mounting flange 104 attached to achimney exhaust pipe 102 of a wood-burning stove 902, and the ring 202attached to the mounting flange 104. The wood stove monitoring device900 can include the other components that have been described. Themounting flange 104 is positioned vertically along the chimney exhaustpipe 102 in FIG. 9 so that the ring 202 is positioned at least partiallyabove the end of the pipe 102. The wood stove monitoring device 900 canwirelessly communicate with a fresh air intake mechanism 904 of thewood-burning stove 902 to control the opacity of smoke 906 generated bythe stove 902 and exhausted through the pipe 102.

FIG. 10 shows an example method 1000 that can be performed via the woodstove monitoring device 900 to control the wood-burning stove 902 sothat the stove 902 outputs smoke with opacity less than a thresholdamount. The calibration mechanism of the wood stove monitoring device900 can first calibrate the optical sensor 402 of the monitoring device900 (1002). For instance, the motor 704 can rotate the calibration wheel702 through its various semi-opaque regions 804 while the optical sensor402 detects the optical beam 406 output by the optical beam source 404,on which basis the optical sensor 402 is then calibrated.

When the wood-burning stove 902 is being used, the optical sensor 402detects the optical beam 406 output through the smoke 906 exhausted bythe stove 902 through the pipe 102 (1004). The temperature probe 502similarly detects the temperature of the heat exhausted by the stove 902through the pipe 102 (1006). The processing hardware 602 correlates theoptical beam 406 as detected by the optical sensor 402 (i.e., themeasured value output by the sensor 402) with or to the opacity of thesmoke 906 (1008).

The processing hardware 602 can correspondingly generate a fresh airintake control signal based on the correlated opacity and the measuredtemperature (1010). The fresh air intake control signal is generated tomaintain the opacity of the smoke 906 below a threshold level. Forinstance, the signal may correspond to increasing fresh air input by thefresh air intake mechanism 904 of the stove 902 responsive to thecorrelated opacity being greater than a threshold for a predeterminedlength of time in which the measured temperature is greater than aminimum operating temperature of the stove 902. In this respect,increasing fresh air intake just when opacity is greater than thethreshold when the measured temperature is greater than a minimumoperating temperature ensures that the stove 902 has sufficient time toinitially heat up when first being used.

The fresh air intake control signal may further correspond to decreasingfresh air input by the fresh air intake mechanism 904 of the stove 902responsive to the correlated opacity being less than the threshold forthe predetermined length of time in which the measured temperature isgreater than a maximum operating temperature of the stove 902. As such,when the opacity of the smoke 906 is sufficiently low, but thetemperature of the stove 902 is too high, the fresh air intake can bereduced to decrease the temperature of the stove 902. Decreasing freshair, however, can ultimately result in increasing opacity of the smoke906, such that the fresh air intake control signal may later cause freshair intake to increase as noted above.

The communication hardware 604 of the wood stove monitoring device 900thus communicates the generated fresh air intake control signal, such aswirelessly, to the stove 902 (1012). The stove 902 can adjust the freshair intake based on the received control signal (1014). The method 1000is continually performed starting at part 1004 once the initialcalibration of part 1002 has been performed, for each usage session ofthe stove 902. The wood stove monitoring device 900 may be powered by abattery to perform the initial calibration, and then be powered by theTEG stack 208 once the stove 902 has generated sufficient heat. As notedabove, the control signal may additionally or alternatively be used tocontrol a thermal oxidizer or other smoke reduction technology mechanismto reduce the opacity of the smoke. As also noted above, thecommunication hardware 604 may also notify an operator of the stove ofthe opacity of the exhausted smoke, either periodically or when theopacity exceeds a threshold.

The wood stove monitoring device 900 can communicate other informationto an operator as well. As noted above, the monitoring device 900 cancontinually monitor the temperature and opacity of the smoke exhaustedby the stove 902. In one scenario, after a length of time, such asthirty minutes, the temperature may be dropping steadily, while theopacity of the exhausted smoke is low. The monitoring device 900 can onthis basis conclude that the fuel (i.e., wood) within the stove 902 hasbeen depleted. To prevent smoldering and excessive smoking (i.e.,increased opacity exhausted smoke), new fuel should be added to thestove 902 before the temperature drops further. Therefore, themonitoring device 900 can send a signal to the stove 902 or its operatorto indicate when new fuel is optimally added. If the temperaturecontinues to decrease, the device 900 may otherwise conclude that no newfuel has been added.

The techniques that have been described herein thus provide for a woodstove monitoring device that can monitor the opacity of smoke that awood-burning stove generates. The wood stove monitoring device caneasily be fitted to existing chimney exhaust pipes, and may not requireany wires or cabling between the monitoring device and the stove. Assuch, residential users are able to continue to use their wood-burningstoves while satisfying any regulations on smoke opacity.

It is finally noted that, although specific embodiments have beenillustrated and described herein, it will be appreciated by those ofordinary skill in the art that any arrangement calculated to achieve thesame purpose may be substituted for the specific embodiments shown. Thisapplication is thus intended to cover any adaptations or variations ofembodiments of the present invention. It is manifestly intended thatthis invention be limited only by the claims and equivalents thereof.

I claim:
 1. A wood stove monitoring device comprising: a mounting flangemountable to and fittable over a chimney exhaust pipe of a wood stove,the mounting flange movably positionable vertically along the chimneyexhaust pipe; a ring removably mountable on top of the mounting flange,the ring having an interior surface and a plurality of exterior flatsurfaces, the mounting flange suitably positionable vertically along thechimney exhaust pipe so that the ring is positioned at least partiallyabove an end of the chimney exhaust pipe; an optical beam sourcedisposed on a first exterior flat surface of the exterior flat surfacesof the ring, the optical beam source generating and outputting anoptical beam perpendicular to the first exterior flat surface andthrough a corresponding hole within the first exterior flat surface andthe interior surface of the ring; an optical sensor disposed on a secondexterior flat surface of the exterior flat surfaces of the ring oppositeto the first exterior flat surface, the optical sensor linearly alignedwith the optical beam source to detect the optical beam output by theoptical beam source as the optical beam passes through smoke exhaustedby the wood stove through the chimney exhaust pipe; and a temperatureprobe disposed on a third exterior flat surface of the exterior flatsurfaces of the ring and extending through the third exterior flatsurface and the interior surface of the ring, the temperature probemeasuring a temperature of heat exhausted by the wood stove through thechimney exhaust pipe.
 2. The wood stove monitoring device of claim 1,wherein the wood stove monitoring device is to correlate the opticalbeam through the smoke as detected by the optical sensor to an opacityof the smoke exhausted by the wood stove through the chimney exhaustpipe.
 3. The wood stove monitoring device of claim 2, wherein the woodstove monitoring device is further to generate a control signal based onthe correlated opacity and the measured temperature, and wherein thecontrol signal controls the wood stove to maintain the opacity of thesmoke exhausted by the wood stove through the chimney exhaust pipe belowa threshold level.
 4. The wood stove monitoring device of claim 3,wherein wood stove monitoring device is to generate the control signalto increase fresh air input by a fresh air intake mechanism of the woodstove responsive to the correlated opacity being greater than thethreshold for a predetermined length of time in which the measuredtemperature is greater than a minimum operating temperature of the woodstove.
 5. The wood stove monitoring device of claim 4, wherein the woodstove monitoring device is to generate the fresh air intake controlsignal to decrease fresh air input by the fresh air intake mechanism ofthe wood stove responsive to the correlated opacity being less than thethreshold and the measured temperature being greater than a maximumoperating temperature of the wood stove.
 6. The wood stove monitoringdevice of claim 3, further comprising: wireless communication hardwareto wirelessly transmit the control signal to the wood stove.
 7. The woodstove monitoring device of claim 1, further comprising: a thermal energygeneration stack disposed on a fourth exterior flat surface of theexterior flat surfaces of the ring, the thermal energy generation stackgenerating electrical power responsive to heat exhausted by the woodstove through the chimney exhaust pipe, wherein the optical beam sourceand the optical sensor are powered by the electrical power that thethermal energy generation stack generates.
 8. The wood stove monitoringdevice of claim 1, further comprising: a calibration mechanism providingdifferent prespecified opacities to permit calibration of the opticalsensor via the optical beam source outputting the optical beamselectively and individually through the different prespecifiedopacities.
 9. The wood stove monitoring device of claim 8, wherein thecalibration mechanism comprises: a calibration wheel rotatably disposedon the ring and having a plurality of regions including a plurality ofsemi-opaque regions corresponding to the different prespecifiedopacities and a transparent region, an active region of the calibrationwheel being a current region of the semi-opaque region and thetransparent region that is in an optical path between the optical beamsource and the optical sensor; and a motor attached to the calibrationwheel to rotate the calibration wheel to select one of the semi-opaqueregions and the transparent region as the active region, wherein duringcalibration of the optical sensor, the motor rotates the calibrationwheel so that the active region in the optical path through the opticalbeam source and the optical sensor proceeds through the semi-opaqueregions while the optical beam source outputs the optical beam, andwherein during operation of the wood stove monitoring device to monitoropacity of the smoke output by the wood stove through the chimneyexhaust pipe, the motor rotates the calibration wheel so that the activeregion in the optical path is the transparent region of the calibrationwheel.
 10. A wood stove monitoring device comprising: a mounting flangemountable to and fittable over a chimney exhaust pipe of a wood stove,the mounting flange movably positionable vertically along the chimneyexhaust pipe; a ring removably mountable on top of the mounting flange,the ring having an interior surface and a plurality of exterior flatsurfaces, the mounting flange suitably positionable vertically along thechimney exhaust pipe so that the ring is positioned at least partiallyabove an end of the chimney exhaust pipe; an optical beam sourcedisposed on a first exterior flat surface of the exterior flat surfacesof the ring, the optical beam source generating and outputting anoptical beam perpendicular to the first exterior flat surface andthrough a corresponding hole within the first exterior flat surface andthe interior surface of the ring; an optical sensor disposed on a secondexterior flat surface of the exterior flat surfaces of the ring oppositeto the first exterior flat surface, the optical sensor linearly alignedwith the optical beam source to detect the optical beam output by theoptical beam source as the optical beam passes through smoke exhaustedby the wood stove through the chimney exhaust pipe; a temperature probedisposed on a third exterior flat surface of the exterior flat surfacesof the ring and extending through the third exterior flat surface andthe interior surface of the ring, the temperature probe measuring atemperature of heat exhausted by the wood stove through the chimneyexhaust pipe; and processing hardware to: correlate the optical beamthrough the smoke as detected by the optical sensor to an opacity of thesmoke exhausted by the wood stove through the chimney exhaust pipe; andgenerate a control signal based on the correlated opacity and themeasured temperature, the control signal controlling the wood stove tomaintain the opacity of the smoke exhausted by the wood stove throughthe chimney exhaust pipe below a threshold level, to increase fresh airinput by a fresh air intake mechanism of the wood stove responsive tothe correlated opacity being greater than the threshold for apredetermined length of time in which the measured temperature isgreater than a minimum operating temperature of the wood stove, and todecrease fresh air input by the fresh air intake mechanism of the woodstove responsive to the correlated opacity being less than the thresholdand the measured temperature being greater than a maximum operatingtemperature of the wood stove.